Poizner, to separate himself from Whitman, made immigration the defining issue of his campaign. He expressed strong support for the controversial Arizona immigration law and attacked Whitman for opposing it.

Poizner criticized the decision by the City of Los Angeles to boycott Arizona businesses to protest the immigration law. He pledged to require all state contractors to provide proof of their employee's immigration status, boycotting any firms that have hired illegal immigrants.

Whitman, who consistently led Poizner in the polls, sought to show that while she opposed the Arizona law, she was not weak on illegal immigration. In her own television advertising, she promised "to secure our border with absolutely no amnesty," as part of her effort to "save California."

The immigration debate could compromise Republicans' chances of winning in November. Hispanics comprise approximately 37 percent of California's population and candidates cannot afford to alienate Latino voters, a large majority of whom oppose the Arizona law and favor earned legalization.

In the fall, Whitman will face Democrat Jerry Brown, the state's Attorney General, who served as governor from 1975 to 1983.

Funding could be a challenge for Brown. The GOP primary has seen massive levels of spending, with Whitman spending over $60 million of her own money and $80 million overall, and pledging to spend up to $150 million of her own money in the general election.

Electability Key Factor in Senate Race

Fiorina received an unexpected boost from the endorsement of former Alaska governor Sarah Palin, even though DeVore was supported by Tea Party groups.

Palin recorded a telephone message for Fiorina, urging voters to "help get our country back on track" by voting for the former executive.

Fiorina spent a lot of her own personal wealth on the campaign, a point likely to be seized upon by Democrats in the midterm elections. Campbell struggled to keep pace, temporarily withdrawing television advertising last week. A libertarian on most social issues, Campbell focused his rhetoric on his electability in the final days of the campaign.

In November, Fiorina is likely to face a heated battle with Boxer, who has been in the Senate for 17 years.

Proposition 14

Today's primary election in California will be the last of its kind, with the passing of a ballot initiative that will dramatically change the electoral process and open the possibility of general election contests limited to two members of the same party.

Proposition 14 would replace party primaries with a "top-two" election structure for congressional, statewide and state legislative elections. All candidates would be included in a single primary election open to all voters, regardless of party registration. Candidates would have the option to declare a party preference or appear on the ballot with no affiliation.

The two candidates with the highest vote totals in the primary would then advance to a general election. Write-in votes would be ignored. The November ballot thus could feature two members of the same party as the only options.

All of California's six ballot-eligible political parties, the state's ACLU groups, and many state labor unions lined up against Proposition 14, while business groups, the California AARP, and a majority of the state's major newspapers endorsed the measure.

The most prominent backer of the proposition was Schwarzenegger. He raised money for the measure and cited the gubernatorial primary battle between Whitman and Poizner as emblematic of the type of primary partisanship that would be eliminated under the proposed system.

Supporters said the initiative would lead to more moderate elected officials and alleviate the gridlock that has characterized the state's politics in recent years. Some raised concerns over the lack of a way to replace candidates on the general election ballot under the proposed system. The two candidates with the highest vote totals in the primaries would appear on the November ballot unless one of them were to die, in which case the third-leading primary candidate would take the open spot.

Proponent groups' fundraising dramatically outpaced that of opponents, with late May numbers from the California secretary of state's office showing a margin of approximately $4 million to approximately $200,000.